1. Field of the Invention
The invention relates to a method and apparatus for connecting different processors to a single computer system board.
2. Description of the Related Art
As microprocessors (or simply processors) have become faster, more powerful and feature laden the electrical and physical interfaces to these processors have also changed. For example, the Intel Pentium is different from the Intel Pentium Pro processor which is different from the Intel Pentium II processor. Future processors are also likely to have their differences.
In the past, system boards were designed to support only one type of processor. To overcome this limitation, Intel developed upgrade processors for each of its standard processors. These upgrade processors would typically plug into the same socket as that of the processor it was replacing. For example, a Pentium processor can be upgraded with a Pentium upgrade processor. The system board included a socket for the processor or upgrade processor. Alternatively, the system board would include a separate socket for the upgrade processor. However, this limited the upgrade capability of the computer system to the number of processors available that met the specification for the existing socket. Thus, to effectively upgrade an existing processor the upgrade processor had to meet the existing physical and electrical requirements.
Alternatively, the existing system board could be replaced with a new system board containing a higher performance processor not available as an upgrade processor. Replacing the system board usually provides better performance gains than simply upgrading the processor. However, this method is less desirable due to the complexity and added cost involved in exchanging system boards.
Another variation known in the art is to partition the system board into two different boards. One board for supporting the system logic and another board for supporting the processor. A Compaq SystemPro is one example. Typically, the processor board would contain much of the logic related to keeping the processor performing at optimum speed, such as memory cache and related logic. In this way, an upgrade was implemented by replacing only the processor board. This method had the advantage of overcoming he limitation brought about by relying on the processor upgrade. However, each supported processor would require a new processor board design.
It is desirable to support a single system board with a wide variety of processors and future processors, but in a cost effective manner.